1. Field of the Invention
This invention relates to an apparatus and method for processing imaging signals. More specifically, the invention relates to an image signal processing apparatus and method which has application in medical or industrial computer tomography, supersonic crack detection, radar equipment, etc.
2. Description of the Related Art
In apparatus for processing imaging signals, geometrical conversion of an input image, such as magnification, reduction, rotation or parallel movement is often performed. FIG. 8 is a block diagram of a well-known processing apparatus.
This image processing apparatus includes an input interface 81, memories 82 and 83, a specialized signal processor 84, an output interface 85 and a system controller 86. A digital image signal from an imaging device, such as a CCD camera, is supplied to memory 82 through input interface 81 and data bus 8A. Memory 82, which has a capacity equal to at least one frame, stores a digital image data corresponding to a level of the image signal. Signal processor 84 reads the digital data from either memory 82 or memory 83, processes the digital data to obtain a desired image, and stores the data in the other of memories 82 and 83. Moreover, processor 84 converts the addresses of the digital data as stored in memory 82. That is, processor 84 calculates a new address, for memory 83 at which the digital image data is to be stored, for each picture cell, to execute geometrical conversion of the image as it is transferred from memory 82 to memory 83. This address conversion corresponds to a conversion of coordinates of the image. The digital data stored at the converted address in memory 83 is supplied to a data output means (not shown), such as an image displaying device, through data bus 8A and output interface 85. System controller 86 controls interfaces 81 and 85, memories 82 and 83 and signal processor 86 through a control bus 8B.
One typical type of geometrical conversion of image data is called an affine conversion which is a first order conversion (variables need not be raised to any power greater than one). Usually processor 84 can only perform first order conversions of geometrical data because the calculations for higher order conversions is complicated. Also, various processes, such as writing data as radius vectors in a memory and adding data following a rotation, are used in synthetic aperture processing for underground survey radar, supersonic crack detectors and in geometrical conversions for industrial X-ray CT equipment etc. Even these first order processes are very difficult because memory 82 usually stores data corresponding to orthogonal coordinates, even if the process is simple in polar coordinates. As a result, processing speed deteriorates.